Squeezing of electro-magnetic field, which is a purely quantum phenomenon has attracted considerable attention owing to its low noise property with applications in high quality telecommunication. This quantum effect is expected to manifest itself in optical processes in which the nonlinear response of the system to the radiation field plays an important role. In this paper squeezing of electro- magnetic field in some multi-photon processes are investigated under short-time approximation. The processes studied include Raman and hyper Raman processes and sum- frequency generation. The coupled Heisenberg equations of motion for field operators are set up and solved under short-time approximation. The occurrence of squeezing of field is investigated using the required conditions of squeezing in each of the cases. The squeezing is found to exist in the fundamental mode and the squeezing in the generated field depends on squeezing in fundamental mode. Squeezing in higher order amplitudes are also studied. This corresponds to the squeezing of the variables which describe the real and imaginary parts of square and cube of the complex amplitudes of the radiation field. The higher order multimode sum squeezing of radiation field is dealt with for harmonic and sum frequency generation. It s shown that squeezing in the sum frequency field depends directly on the sum squeezing of fundamental modes. The results can be utilized in selecting a suitable process which will generate a radiation field with optimum squeezing and can be useful in high quality telecommunication.
This paper provides a mathematical analysis to calculate the number of longitudinal modes and their relative strength in a dye Q-switched ruby laser. The calculations were based on formulae developed to accurately predict the number of loop transmits that occur while the laser pulse builds up from noise levels. An experiment was carried out using a ruby laser set-up to confirm our theoretical predictions. The number of longitudinal modes present in the laser output was evaluated by recording holograms of a two meter long graduated panel using the same laser source. The end results closely matched our theoretical predictions. This proven mathematical analysis was then applied to our laser design to optimize the longitudinal mode selection property of the dye Q-switch in the laser. As a result, the developed ruby laser produced single longitudinal mode pulses at a probability of 98%.
Beam quality improvement of high power solid state lasers for industry and science is a crucial point. A simple way to increase the beam quality of conventional flash lamp pumped rod systems is to use a phase conjugating mirror based on stimulated Brillouin scattering (SBS). Pulsed multi amplifier setups with SBS were investigated. Nd:YALO as active material was used to avoid stress birefringence and decrease of beam quality. In case of serial arrangements on optimized optical system between the individual rods is used to achieve high efficiency independent of thermal lensing. With a two amplifier system an average output power of 1 Watt up to 210 Watt in a near diffraction limited beam was realized. In case of parallel arrangements phase coupling of the individual beams was achieved using a common SBS-cell after the first amplifier pass. First experiments show an average output power of 50 W. CW-pumped MOPA-systems with SBS and repetition rates above 10 kHz are under development. A fiber phase-conjugator is used to reduce the power threshold down to 6 kW. An average output power of 14 Watt from a pulsed MOPA-system was achieved with a fiber phase- conjugator. As an application high power second harmonic generation was realized.
The paper presents the design of a dichroic mirror used in a Nd:YAG high power laser to reflect the 1.44 micrometers radiation and to transmit the 1.064 micrometers one. In order to obtain a wide transmission band, all the solutions for matching basic stack with the substrate, consisting in a number of periods less or equal than three, were investigated and the best was selected. The solutions were obtained by analytical inversion of the equations for the three layer equivalent system.
Optical components which highly reflect the hydrogen fluoride (HF) overtone wavelengths (near 1.3 micrometers ) and transmit or absorb the HF fundamental wavelengths (2.6 to 3.1 micrometers ) can be used to obtain high intensity 1.3 micrometers radiation with HF chemical laser technology. This paper describes the development of the HF overtone laser resonator mirrors. Also presented are the designs of the coatings for laser resonator and the optical performance results for the coatings which includes separated coatings that are highly reflected in 1.3 - 1.4 micrometers wavelengths and highly transmitted or low reflected in 2.6 - 3.1 micrometers wavelengths and the double band antireflection coating for 1.3 - 1.4 micrometers and 2.6 - 3.1 micrometers .
Two sorts of microchip laser materials, such as Nd:YVO4 and Er/Yb:Cr phosphate Kigre glass, are used to perform the experimental study of pump absorption saturation. A spatial- dependent rate equation model has been developed for the simulation, and hence the corresponding absorption saturation intensities are determined, the pump saturation intensity is 840 W/cm2 in the (pi) -polarization, and 2200 W/cm2 in the (sigma) -polarization for the 3% a-cut Nd:YVO4 crystal for the 810 nm pump wavelength, and 130 kW/cm2 for Er/Yb:Cr phosphate Kigre glass for the 975 nm pump wavelength. Based on this nonlinear absorption effect, a high performance LD end-pumped Nd:YVO4 microchip laser was obtained with a low pump threshold of 3 mW and a high slope efficiency of 50%, while for Er/Yb:Cr phosphate Kigre glass laser, a low pump threshold of 5 mW and 20% slope efficiency was obtained when pumped by a Ti:Sapphire laser. All the laser operated in a single transverse mode, and the 1.535 micrometers laser operated at a single longitudinal mode. This study gives a useful guideline to design and to optimize the pump beam radius of LD end-pumped microchip lasers.
A useful model has been developed for the optimization of fiber-coupled laser-diode pumped lasers by including the effect of pump beam quality into the mode overlap integrals. Simple analytical expressions for the optimum pump spot size, the threshold pump power, and the slope efficiency have been derived by fitting the numerical results of the mode overlap integrals to an analytical function which is in terms of laser-diode beam quality and properties of the active medium. With these expressions the optimum mode size and the maximum output efficiency can be calculated for arbitrary values of pump beam quality and input power. Also, we obtained an analytical expression to relate the required input power and pump beam quality to the desired output efficiency and properties of an active medium. The present model provides a straightforward procedure to design the laser resonator and the optical coupling system for output optimization. To illustrate the utility of the present model, a Nd:YAG laser pumped by fiber-coupled laser diodes is considered and optimized. Experimental results have shown a fairly good agreement with the theoretical predictions.
Multipass Ti:sapphire amplifier for the light source of DIAL was developed in an angular-multiplexing, and the characteristics of output energy and spectrum was investigated. In the two-stage multipass amplifier, we obtained the maximum output energy of 42 mJ, the amplification gain of 21 dB and the output efficiency of 26% on the wavelength of 790 nm. In the tuning range of 715 approximately 930 nm the spectral linewidth is 0.05 cm-1. The conversion efficiencies of 35% for SHG at 780 nm and 13% for THG at 390 nm are obtained respectively. The continuous tunabilities of 240 approximately 306 nm in UV region and 360 approximately 460 nm in deep-blue region could be achieved.
We have developed an excimer laser of compact coaxial type which the one line cross flow fan is only used. At 1 kHz repetitive operation, the average power of KrF laser is 56 watt. In this paper, the design parameters and CR characteristics are investigated for the attainment of the 1 kHz excimer laser. We have obtained the overall efficiency of 1.2% with KrF laser gas. At this time, CR and the variation of laser output are 2.97, +/- 9%, respectively. Laser gas volume and active volume are 10 liter, 1.8 (H) X 1.2 (W) X 30 (L) equals 64.8, respectively.
Temporal methods of fringe analysis have been used to measure transient effects due to high average power thermal loading in solid-state optical crystals. Studies using a dual-interferometric configuration have revealed non-uniform and non-reciprocal lensing to be a significant source of error in the output fringe patterns. This study isolated and quantified the impact of such lensing with respect to interferometric analytic techniques.
The model developed allows to know the temperature field in a cw Nd:YAG laser joining piece. To realize the model, a physical approach has been used for defining the heat sources. First, from a pressure balance the geometry of the keyhole is determined. Then, an analysis of the plume existing at the surface of the target shows that the beam is scattered by the plume and consequently one more heat source must be considered. The spectrometric characterization indicates that no ionized particles exist in the plume and certainly in the keyhole. So Fresnel absorptions must be the predominant effects for energy absorption in the keyhole. This assumption has been verified owing to Fresnel absorption coefficient measurements.
A prototype of ridge-waveguide type microwave pumped systems versatile to both CO2 and CO lasers has been adopted to a compact fast-axial flow scheme. Dependence of the output power Pout on total gas pressure p, microwave power Ppump and gas-flow velocity (nu) is investigated for both the lasers, together with the effect of (nu) on gas temperature T. The maximum output powers of 42 W and 15 W are, respectively, obtained with the discharge lengths of 11 cm and 37 cm for CO2 and CO lasers, corresponding to the scaling-powers of 380 W and 38 W to a unit discharge length. Since the ridge-waveguide is, thus far, not optimized yet, there is still some room in CO laser to be modified for effective pumping, involving the direction of gas-flow.
Effects of mirror expansions to obtain higher power from an unstable resonator are proposed. Calculations are performed for expanding radius of a concave or a convex mirror to reduce the diffraction loss power from the concave mirror and to convert the power spread out from it into the output power. The Fresnel-Kirchhoff formula is used for the iterative computer calculation in the passive resonator and a CO2 laser. The calculations show that the increase of the output power can be obtained more than 25 percent with expanding the convex mirror in the CO2 laser.
Stimulated Brillouin Scattering (SBS) as a phase conjugate mirror is successfully used in high power solid state laser system due to its self adaptive character and his simple step without optical damage in SBS medium. In oscillator and in amplifier with the SBS phase conjugate mirror the output beam quality has been improved. The beam quality with the diffraction limit and high power were obtained.
The fundamental concepts and developments of solid-state slab laser technology is briefly reviewed. The performance of the high average power zigzag Nd:YAG slab laser facility having been established at NCRIEO is presented. Experiments with several slabs of different dimensions and qualities were performed and the results of two of them are presented. Stable, cylindrical and spherical unstable resonator configurations were tested. When the devices worked at a repetition rate of 50 Hz and the pumping pulse energy of 307 J, the maximum output from a cylindrical 1D unstable resonator is 690 W with a total efficiency of 4.5%. The divergent angle is 3.6 X 0.5 mrad in Y and X directions respectively corresponding to about 10.8 X 1.62 times diffraction limit and a beam parameter product d0/4 about 5.5 X 0.75 mm.mrad in Y and X directions respectively. The device worked continuously at above 630 W output level for an hour. When the device worked at a repetition rate of 100 Hz, the maximum output power was 520 W.
In this paper, we present a simple and easy-use geometrical approach for designing the unstable resonator of Nd:YAG laser with a Gaussian output coupler. An equivalent rear mirror, which formed a confocal resonator with the output coupler, was introduced to include the effects of rear mirror, the thermal focus of YAG rod and optical path of Q- switch. Numerical results were calculated for various couples of matching curvatures of rear mirror and output coupler under the confocal condition. The correspondent optimal spot sizes of the output coupler were also given. Couples of mirrors were selected according to theoretical parameters and applied to the experimental setup. A high- beam-quality output with Gaussian profile, and high efficiency of second harmonic generation were obtained. The experimental results were in good agreement with theoretical prediction.
A novel structure FP cavity erbium-doped fiber laser is reported in this paper. The passively Q-switched operation of the laser has been achieved by using a bulk semiconductor waveguide as a saturable absorber. Under 15 mW pump power, pulse of 2 microsecond(s) full width at half maximum and peak power close to 22 mW has been obtained.
This report deals with a simple method to tune the pulse- width for a single-mode Q-switched YAG oscillator by simply changing the inner distance of two-cell stimulated Brillouin scattering (SBS) systems. The SBS pulse is amplified as it returning into the YAG medium and then output coupled by a quarter wave-plate and a cavity polarizer. This double-pass phase-conjugate configuration improves the laser beam quality. Less than 2 times diffraction-limited divergence is achieved. Pulses with 2 - 8 ns tunable range and about 10 mj pulse energy are obtained.
Recently, high beam quality, large energy pulsed lasers with variable reflectivity mirrors has increasingly applied in nonlinear optics, scientific research lidar, industry manufacture, and military etc. To obtain high beam quality and efficient extraction simultaneously from an unstable resonator, the super Gaussian mirrors peak reflectivity R0, the super Gaussian order n, and the round-trip magnification M are three key parameters which must be carefully selected. In this paper, intensive investigation on beam quality of unstable resonators with VRM affected by R0, n, M, R0Mn is presented by computer simulation. A optimum design resulting near diffraction limited beam quality, large energy, high repetition is obtained. Various VRM tested in Q-switched Nd:YAG lasers pumped by flashlamp. Less than 2 X LD, 6 ns, 40 Hz, 350 mj/pulse laser beams are obtained in single oscillator, more than 1 J/pulse is realized through one amplifier. The experimental results are in good agreement with the optimum design.
Thermal focusing acts as a key role in limiting and degrading the laser performance in a continuously end-pumped solid-state laser. In order to evaluate the deleterious effect caused by thermal lensing in such a laser scheme, heat transfer equation is solved to obtain the temperature distribution in an edge-cooled and axially Gaussian beam heated rod in the form of a power series, taking into account only the radial heat flow, which is a reasonable simplification of the real situation. Also, under the two assumptions of thin disk and long rod, the induced stress- and strain-field are deduced, respectively. Thus the analytical expressions for the induced thermal focusing length are determined over the extent of axially average pump spot size, considering all the following three elements contributing to thermal focusing: thermal dispersion, surface deformation and stress-induced birefringence, and regarding the rod as thin lens and thick lens, respectively. The results are applied to cubic crystals, such as Nd:YAG and Nd:GSGG, and the homogeneous medium of silicate Nd:glass. It can be seen that with ten watt of pump power, the effective focusing lengths of these materials are in the order of millimeters and much more serious than those predicted by other authors.
Based on the nonlinear ABCD matrix and the renormalized q- parameter for Gaussian-beam propagation, self-focusing in conjunction with a spatial gain profile for self-mode locking in a ring-cavity Ti:sapphire laser are analyzed. In the experiment, an astigmatism-compensated self-mode-locked ring-cavity Ti:sapphire laser is demonstrated, and self- mode-locked operation is achieved in both bidirection and unidirection with pulse durations as short as 36 fs and 32 fs, respectively. The experimental observations are in good agreement with theoretical predictions.
In this letter we report the use of intracavity frequency doubling in a self-mode-locked Ti:sapphire laser to generate violet-blue light ultrashort pulses at a repetition rate of 82 MHz. Our Ti:sapphire laser can produce 100 fs pulses at a wavelength of 780 nm. By frequency doubling in a 1-mm-thick lithium triborate crystal we generate 25 mw violet-blue light in each of two ends from the laser. This laser will make it possible to extend ultrafast techniques to a new spectrum regime.
Stability of Ti:Sapphire laser is researched in the paper. The experimental results and theoretical analysis show that the instability of the output is contributed to the pump stability, the quality of the crystal, and the spontaneous emission photon numbers that enter into stimulated emission modes, which we believe is put forward for the first time.
Three reference systems for the calibration and comparison of beam parameter measurements and beam quality of cw and pulsed lasers at NIM are described. While the cross- sectional power/energy density distribution function of TEM00 He-Ne laser and pulsed Nd:YAG laser are detected by a CCD-camera, the power density distribution function of cw CO2 laser is scanned by a liquid nitrogen cooled TeCdHg detector. Test procedures and evaluations are referred to ISO/DIS 11146 document. From the measured cross- sectional distribution function, the first and second spatial moments as well as the beam width are calculated. The waist location and width are determined by a hyperbolic fit to different measurements of the beam width along the propagation axis. The error evaluation equations for beam parameter measurement have been derived. Measurement agreements using different test methods and instruments are studied. Varieties of beam characteristics and measurement uncertainty for two measuring apparatus are given.
Aberrative nonlinear transfer matrices are introduced to treat the propagation of laser beam in Kerr medium with thermal lensing. The dependence of mode-locking regions on cavity symmetry and the distance between the fold mirror and the crystal, and the optimal agreement for Kerr-lens mode- locking are discussed with ABCD matrix method.
Basic properties of the concave-convex stable resonator (CCSR) with cavity parameter g1g2 near to 1 are discussed in the infinite aperture approximation. The field distributions and diffraction losses of the low order transverse modes of related resonators with finite aperture are analyzed numerically. The stability of the output power of the lasers with CCSR are studied experimentally. We have made a total of 120 red internal mirror He-Ne lasers with CCSR (g1g2 >= 0.90) whose cavity lengths are approximately 63 cm and the effective lengths of discharge tubes are about 52 cm. Most of the lasers operate with TEM00 stably, and the highest output power is 30 mw. The laser beam waist lies outside the resonator at a distance of 1.0 m from the concave mirror, and the beam divergence is 0.45 mrad. For the TEM00 lasers operate normally, the misalignment angle of the resonator mirrors must be less than 10-5 mrad. The following facts are of particular value. (1) When the resonant frequency spacing between two successive transverse modes of a CCSR (Delta) (nu) is so small that its effect on the competition among transverse modes in the lasers with the CCSR can be negligible, we call such a CCSR near critical CCSR (NCSR). It is observed that even if the round trip total loss (including the transmission loss and so on) of TEM00 is only about 0.2 round trip small signal gain of the laser, and the round trip diffraction loss of TEM00 is only about 0.001, still the laser with the NCSR operate with pure TEM00 stably. It is clear that the mode competition in a laser with NCSR is extraordinarily favorable for TEM00$. (2 While the TEM00 lasers operate normally, the center frequency of every longitudinal mode is stable, its drift per hour is less than 0.1 longitudinal mode spacing (approximately equals 2.4 X 107 Hz). (3) The superradiant transition at 3.39 micrometers is suppressed.
An approach to the design and fabrication of the mirrors for a new type 1300 nm He-Ne laser is described. In addition to special reflectance at the central wavelength, these mirrors must be not only hard surface with lower loss, but also narrowband, and have lower reflectance at 1150 nm, 1500 nm, 1700 nm, 3390 nm wavelength and so on. Moreover, optical coatings on the mirrors can withstand high temperature.
Different geometry nozzles used in CW hydrogen fluoride chemical laser are investigated. Four geometry parameters, including throat width; area ratio; axis length and base width are considered. The flow properties, laser outcoupling power and small signal gain (SSG) of a Fabry-Perot resonator are calculated. The results show that when throat width and area ratio increase, the power and SSG peak will decrease in varying degree; they also varied when axis length changed; larger base width is related to lower cavity pressure, and smaller base width is related higher cavity pressure.
In this paper, an optical system is described that is an optical head of a coherent imaging CO2 laser radar. Discrimination and field of regard limit decided by the optical head itself are discussed. In the experimental laser radar only one continuous wave, single mode CO2 laser is used, and the signals from buildings of 7 km away are obtained with acceptable SNR while the laser output is about 5 w. Furthermore, the comparison between two optical systems based on individually linear frequency modulation (or chirp) pulse compression and frequency modulated continuous wave technique is also introduced in this paper.
In this paper, we first demonstrate that the signal received from the laser underwater target detection system may be chaotic through phase space reconstruction, correlation dimension analysis and Lyapunov exponent calculation. Then the result of the correlation dimension analysis is used to construct a neural network predictor which is considered as an approximation of the basic dynamics of the received signal. Finally we introduce a chaos-based detection method and apply it to detect the underwater target. The performance of this new method is superior to that of the conventional method.
In this paper, we report the `Ultraviolet-Visible-Infrared Wide Band Tunable Pulse Laser' has been used in identifying the criminal's fingerprint. Different contaminator and secretion of fingerprint in different carrier can be reappeared by illuminating with different wavelength of laser beam. Separating off the laser beam from its induced fluorescence beam with different optical filter, the clear high signal noise ratio fluorescence picture is obtained in a dark background. A series of fluorescence fingerprint picture excited by different wavelength laser light is taken in our Lab. In addition, by using the wide band tunable laser, we test different fluorescence powder or reagent, which sensitivity in different wavelength, a lot of clear fluorescence picture is taken by correspondent wavelength laser beam injection. In this way, the wide band tunable laser offers a wide band of wavelength for develop high sensitivity new fluorescence powder or reagent in chemical field.
In some applications of optical phase conjugation in laser beam propagation in the atmosphere, the method of active beam light is used, in which a probe light is transmitted to the target and the reflective light acts as the beacon light. Generally, it is believed that the reflective area on the target must be small enough to be regarded as an unresolved glint, and this limits the application. In this paper, the effect of the reflective area on the optical phase conjugation is discussed, and an experiment by means of nonlinear optical phase conjugation using a ruby laser, Stimulated Brillouin Scattering is an acetone device and a hole to change the reflective area is made. We demonstrate that, the wavefront of light can be restored correctly on the target. In the case of motionless target, the limitation of the reflective area must be satisfied, otherwise the amplified phase conjugated light on the target will return to the probe light source and damage it, whereas, in the case of the remote and high speed moving target, because the reflective place on the target is changed during the period of phase conjugation, the light is only reflected on the target, and so the area may be larger than the limitation.
The surface micro-deformations of a cavity copper mirror, an annular channel copper mirror, a multi-layer copper mirror and a sandwich copper mirror are tested when the mirrors are irradiated by high power laser and cooled by water. The test result shows that the surface deformation values of the multi-layer copper mirror and the sandwich copper mirror are much smaller than the cavity copper mirror and the annular channel copper mirror, and the multi-layer and the sandwich copper mirror can meet the requirement of a high power laser system on very small mirror surface deformation.
We report here LD pumped Q-Switched LNYAB Self-frequency-doubling Laser. Under 570mW of O.8O2.tm pumping power, the series pulses of O.53j.im green laser with 4.2ns of pulse width and 750W of peak power have been measured . The laser reliably operates when Q—switching rate ranges from CW to 100kHz. The highest peak power was obtained at repetition rate of 10kHz. To our knowledge, it is the first LD pumped acoustooptic Q-switched LNYAB green laser in the world and should be a desirable and reliable pulsed green laser source in the future.
KEY WORDS: Self-frequency-doubling Laser, LD Pumped, LNYAB, Q-Switched
An ultraviolet laser has been developed from the 632.8 nm line of a Helium Neon laser using internal frequency doubling method with a Lithium Iodate crystal. It generates continuous ultraviolet radiation at 316.4 nm. By optimizing the optical components, a folded three-mirror resonator gave out UV radiation up to 1.5 mW.
Potassium Titanium Oxide Phosphate (KTP) is a new nonlinear frequency-conversion crystal. It has high nonlinear coefficient, high damage threshold, easily-polished surface, and a broad transparency range. In this paper, the calculation method of angle phase-matching for parametric generation in KTP was presented. The angle phase-matching curve and their characteristics in KTP pumped by 532 nm, 694.3 nm radiation were calculated and analyzed. The propagating principal plane (x-y plane) and 56 degree(s) cut angle to z-axis were selected in our experiment, and the measured results agreed well with the calculated ones. The quality of laser beam is an important factor of affecting OPO threshold fluence and conversion efficiency, so the phase-conjugate technology of Stimulated Brillouin Scattering (SBS) for improving the pump laser beam quality was discussed and applied to the pump laser system. The tuning curves and output energy of KTP OPO pumped by Ruby laser (0.6943 micrometers ), the second harmonic of Nd:YAG (0.532 micrometers ) were measured and compared with the theoretical cases. An important result was obtained that the amplified back SBS light which was employed to pump KTP OPO could greatly reduce the OPO threshold.
By means of studding on the characteristics of phase mismatch of Neodymium yttrium aluminum borate [NdxY1-xAl(BO3)4; NYAB] crystal, a method of improving beam profile of NYAB laser was presented. Because of the exist of little, periodically local shortcomings of NYAB crystal, there were different wave-vector mismatch (Delta) Ks at the different locations of NYAB when a wide incident beam passed through it for SHG. According to the phase matching theory of second harmonic generation, there were different conversion efficiencies at the different locations of the incident beam, resulting in inhomogeneous beam profile of second harmonics. We measured the curves of the SHG efficiencies versus phase mismatch angles of NYAB crystals under cases of different diameters (100 micrometers - 2 mm) of fundamental wave beam. The curves showed that the phase mismatch acceptance angle (Delta) (Theta) m was very small for the thin incident beam when a very homogeneous harmonic beam was obtained, while (Delta) (Theta) m was large for a wide incident beam and the profile of the harmonic beam was not homogeneous.
We first demonstrate Kerr-lens mode locking of diode pumped Nd:LMA laser by using an additional Kerr medium of large nonlinear coefficient and fast response time. The laser produces 610-fs, 130-MHz pulses at 1054 nm of laser wavelength and 10 mW of average output power. Kerr-lens mode locking is initiated by mechanical perturbation.
The characteristics of a LD-pumped Nd:YVO4 laser operating at 1340-nm are reported. The maximum output power of 157mW with a slope efficiency of 3 1 .5% has been realized at the incident pump power of 515mW. With a KTP crystal for intracavity-frequency-doubling , 3.6 mW red laser at 670-n.m is obtained. Keywords: LD-pumped, Nd:YVO4, intracavity-frequency-doubling
This paper introduces a new method for both producing and stabilizing the frequency difference of a HeNe birefringence dual frequency laser, which employs a PZT to press the intracavity quartz crystal plate according to the difference between objective beat frequency and output beat frequency of the laser.
We describe the mechanism for the nonreciprocal behavior of a traveling-wave A-O modulator. 20 mw single-frequency output for 200 mw pump and 4 (mu) j/pulse are obtained in a ring laser with A-O Q-switch. Finally, we describe a design of monolithic, planar, diode-pumped, single-frequency ring laser with A-O Q-switch.
Natural rubidium is a mixture of the two isotopes, 85Rb and 87Rb. Taking into account their hyperfine structure, and using a quantum-mechanical treatment of the resonant Faraday effect, we calculate the transmission, central frequency shift and pass bandwidth of Rb 780 nm Faraday- Zeeman optical filter, as functions of magnetic field strength and atomic cell temperature.
The successive approximation method was used to stabilize cw laser power. Silicon photodiode is used to monitor the laser output power, and elector-optical modulator is used to control the power. The feedback loop could work in both linear and non-linear states. Thus the time to reach stabilization is shorten and the stability is improved. We experiment with an external He-Ne laser whose own output power is 8 mW and stability is 3%, and obtained stable output power 5.5 mW with stability 0.002%/hour. This kind of laser power stabilizer can also be used in other visible to near infrared laser.
By the principle of double-layer slice the fabrication of adaptive compound electrodes without thermo-curvature is reported first for transversely discharged S2 laser. The fabrication adopts a wide filmy sealing outlet as well as hard-connection between metals and results in electrode parallelism better than 3 X 10-5 in the temperature range of 273 - 673 K and least dynamic impedance.
A novel method for mode optimization of a high-power laser is presented in this paper. A binary optical resonator is formed through introducing binary optical technology into a laser resonator. The traditional spherical mirrors are substituted by binary optical mirrors. Diffraction analyses show that this kind of resonator can construct any modes as desired with a strong ability of mode selecting and optimization. For a high-power CO2 laser, an optimum design of the binary optical resonator is implemented to obtain a fundamental-mode laser output with a uniform intensity distribution.
The ion-channel laser (ICL), which make use of an electromagnetic instability of an ion-focused relativistic electron beam, is a new form of free-electron laser. In this paper, we introduce a cyclotron electron beam into the ion channel and study the circular polarized ion-channel laser (CPICL) with an axial guiding magnetic field. Using 3D fluid theory, the dispersion relation of the CPICL has been derived. A new kind of radiation mode-ion electrostatic gyro-penitron mode--is found, and the growth rate of this new mode has been obtained for the first time. The effect of axial guiding magnetic field on CPICL is also investigated.
Here we present a class of exact pulse solutions of full- wave-equation in free-space. The most important characteristics (faster-than-c propagation and farther-than- J0-beam propagation) of these nondiffraction pulse beam solutions are discussed. The arrangement to create this pulse solution also is considered.
We have developed an imaging theory of interferometer imaging laser radar. This method probes a target using a scanning fringe pattern that is formed by two interfering beams of slightly different frequency on the surface of the probed target, then the received signal on the detector includes the information of the probed object. In other words, the scanning fringe pattern formed on the surface of the probed target is modulated by the characteristics of the object. So an image of the target being probed can be generated from the amplitude and phase of the received signs by taking the inverse Fourier transform of this information. This interferometer imaging laser radar can be superior to the mechanical scanning laser radar in the imaging rate and the spatial resolution.
We select the alloy and glass which match each other in expansion coefficient, which can prevent the corrosive sulfur vapor to make the electrodes and the tube wall, making the transverse discharge electrodes pass through the well sealed tube wall by technique of glass-to-metal high vacuum sealing under the condition of high temperature. The S2 discharge tube of wide transmission lines has been made. The inductance is reduced to 3% and the resistance to 28% compared with existent S2 discharge tube of single- axle transmission lines in the transmission lines.
In this paper, the quenched dye lasers pumped by XeCl and KrF excimer lasers were investigated theoretically and experimentally. Dye laser pulses with duration of 0.8 ns for XeCl laser pumping and 2 ns for KrF laser pumping were obtained.
This paper gives some results and curves from digital calculating about equations of TEA CO2 laser. 3D Chang's electrode was precisely calculated and manufactured to gain well-distributed electric field in discharge space, which is necessary for TEA CO2 laser. A pre-ionization technique used in this laser was described. A gas circulating system was designed to let the laser operate at high repetition frequency (HRF). It is a key technique to extend the operating life of mini high repetition frequency sealed-off TEA CO2 laser. So, an efficient low temperature catalyst is used in this laser. Mini HRF sealed-off TEA CO2 laser can be applied for the military such as rangefinder, tracing, designating, etc. The specifications of this laser are following: mode is TEM00, divergence (whole angle) in far field is less than 4 mrad, pulse energy of TEM00 mode is 87.8 mJ, FWHF is 36.5 ns, peak power of TEM00 mode is more than 0.9 MW, operating frequency is 130 Hz (the maximum frequency is up to 255 Hz and it can operate continuously at 50 Hz), it's operating life is more than 1 X 107 shots.
The characteristics and mechanism of superpulse discharge for high power FAF CW CO2 lasers are based on the rate equation theory. The mathematical modeling analysis of superpulse discharge especially considering the influence of turbulence and convection is simulated on the computer. Detailed mathematical modeling curves which demonstrate how superpulse operation is employed around population inversion, gain and injection power density are obtained. The results are relevant for superpulse CO2 lasers.
Low-frequency amplitude instabilities, called `green problem', were observed in a laser diode array pumped, intracavity-frequency-double Nd:YVO4 laser under certain experimental conditions. The results of an experimental and theoretical investigation of these instabilities are described, and the theoretical analysis agrees fairly well with the experimental observations.
In this paper the lasing performance of a intracavity doubling of CW diode-laser end-pumped Nd3+:Sr5(PO4)3F, Nd:S-FAP, laser with KTP crystal was reported. We measured the single output performance of the green laser: the pumping threshold was 8 mW; when the pumping light of 210 mW was absorbed, the maximum single output at 529.7 nm was 4.4 mW (TEM00 mode), corresponding to a total conversion efficiency 2.1%. The comparison between experimental results and theoretical calculation was also discussed in this paper.
In this paper, the characteristics of monolithic unidirectional planar ring oscillator (PROs) are analyzed, and design criteria for PROs with low thresholds and large nonreciprocities are expounded on the basis of the eigenpolarization theory of monolithic nonplanar ring oscillators. A Nd:BGO PRO is designed to take advantage of its large Verdet coefficient.
Proposed for the first time to our knowledge is a novel scheme of a diode-pumped birefringent dual-frequency Nd:YAG laser, whose resonant cavity contains a piece of versatile element: crystal quartz Fabry-Perot etalon, acting as a mode selector and a mode splitter as well as a reference of stabilizing the frequency-difference. The laser will oscillate simultaneously in two linearly and orthogonally polarized modes spaced 5-GHz, corresponding to a synthetic wavelength of approximately 60-mm, which is well suitable for absolute-distance interferometry. The stabilization of the frequency-difference is also considered in detail.
First, the factors that degrade the beam quality of high average power Nd:YAG lasers are analyzed. Especially the optical asymmetry of Nd:YAG rod under high power pumping is experimentally verified. A novel resonator--the four mirrors resonator is introduced, which has two mechanisms of beam quality improvement: the image-rotating and interference filtering. Experimental results show obviously the effect of beam quality improvement of the new resonator compared with its equivalent plane-parallel resonator under the same pumping power.